This invention relates to flame retardant polyolefin compositions. More particularly, this invention relates to flame retardant polyolefin compositions comprising a polyolefin, a flame retarding amount of the pentate salt of an amino-s-triazine and a polyhydric alcohol, and to a method for rendering polyolefins flame retardant.
Polyolefins are difficult to render flame retardant. A number of halogen-containing flame retardants are known which, when compounded with polyolefins, provide non-burning compositions, i.e. materials which do not propagate flame. However, polyolefins such as polypropylene have a tendency toward dripping flaming drops which is quite difficult to overcome, and such non-burning compositions generally are not capable of being made fully self-extinguishing.
An alternative approach is to incorporate char-forming additives which, in the presence of flame, form a thick, non-flammable insulating barrier to protect the substrate polymer. One such intumescent or char-forming system, disclosed in U.S. Pat. No. 3,936,416, employs a combination of melamine pyrophosphate and a polyol. This additive combination is effective in providing a non-burning, non-dripping polypropylene composition. Preparation and compounding with these materials can be difficult. During preparation, the additive combination must be degassed in order to avoid foaming during the compounding with polypropylene and/or in subsequent molding operations. In addition, the additive as obtained has a substantial tan or brown color which imparts an undesirable hue to the polypropylene compositions, and the additive is obtained as a hard, solid mass which is pulverized with some difficulty for compounding.
The pentate salts of amino-s-triazines are effective intumescent flame retardant additives for polyolefins, providing compositions that are self-extinguishing, intumescent and non-dripping. The additives are dry, white, powdery solids and are readily compounded with polyolefins to provide compositions which have excellent color and which are readily processed without apparent foaming or decomposition. The preparation of these compounds is disclosed in U.S. Pat. No. 4,154,930, and their use in polyolefin compositions is disclosed in U.S. patent application Ser. No. 937,343, filed Aug. 28, 1978, now U.S. Pat. No. 4,201,705.